Nanomaterials and Nanoarchitectures

Colloidal photonic crystals have been attracting much attention due to their novel use as 3D photonic crystals and tunable structural color. The tunable structural color by swelling and strain is demonstrated on examples of opal composites. In addition, a high quality opal film coating process is reported.

An approach for experimental design in plasmon-enhanced spectroscopy is discussed based on its basic elements: electromagnetic radiation, adsorbed molecule and the metal nanostructure. Optimization of the plasmon enhancement may be achieved by tuning the electromagnetic radiation to take advantage of resonances with molecules and nanostructures. For instance, when the excitation is in resonance with a molecular electronic transition, resonance Raman scattering is observed providing a very efficient scattering with cross section for vibrational transitions several orders of magnitude higher than normal Raman. Tuning the excitation of the nanostructure might depend on the degree of aggregation, or the properties of two and three dimensional array of fabricated nanostructures. Several examples of surface enhanced Raman scattering (SERS), SERS and surface enhanced fluorescence using shell isolated nanoparticles are presented. The experimental results illustrate the remarkable optical properties of metal nanoparticles which are governed by the excitation of localized surface plasmon resonances producing local enhancement of the electromagnetic field. However, each experiment is unique and requires a selection of the setting for each one of the three elements that would lead to the most efficient plasmon enhancement.

Recently, we have introduced the new concept of nanoarchitectonics to traditional supramolecular self-assembly to promote the development of the bottom-up approaches. The concept of nanoarchitectonics can be developed using synergic contributions of technical innovations such as atomic/molecular-level control, chemical nanofabrication, and self- and field-controlled organization. This concept might be applied to inorganic, organic, biochemical, and other systems, beyond the levels of substance, material, and system regardless of their dimensions i.e., macro, micro, or nano scale. In this chapter, recent examples of research on functional nanomaterials prepared by nanoarchitectonics-based supramolecular assembly are explained. These examples are classified according to their scale, (i) molecular-level nanoarchitectonics, (ii) microscale assembly, (iii) macroscopic materials with internal nanostructures.

Nanotechnology as a natural continuation of microtechnology introduced a new bottom-up approach in the building of structures. In this paper we summarize a brief history of nanoscience and nanotechnology by documenting the main milestones on the roadmap of this branch since the beginning of the twentieth century. We discuss the new properties of materials and structures appearing in the nanoworld that originate from both classical and quantum phenomena. We provide a critical analysis of inflated versus realistic expectations of the new technology. Attention is also paid to risks and regulations in the field, as well as codes of conduct of responsible nanoscientists and specific aspects of nanoethics that open a new chapter in ethical studies. The study elaborates on five foresight topics covering the building of structures atom-by-atom, the possibilities to close the appearing nano-divide, the future of silicon, single-particle devices, and sustainability in the field and single-particle devices. Among single particle devices the focus is on the transistors and sensors. We also highlight the role of social sciences and humanities in nanoscience and nanotechnology in the fields such as philosophy, psychology, security, the protection of privacy and intellectual property rights. Ethics is the main area of these activities.

Halloysite is a naturally occurring nanometer scale tube that is capable of both enhancing the physical properties of a material and functionalizing the material. The addition of halloysite into polymeric materials increases the composite physical strength because of the shape and stability of these 50-nm diameter and ca. 1,500 nm length tubes. Whereas the unique chemical and physical characteristics of halloysite allow for loading drugs, biomacromolecules, anti-corrosion agents, flame-retardant agents, and metal nanoparticles followed by their controlled release. Therefore, by loading a chemical of interest inside of the tubes and then mixing the modified halloysite with various materials one will not only be able to make stronger materials but make them smarter and provide sustained functionality that would otherwise not be possible.

A brief introduction to photonic crystals and colloidal photonic crystals in particular is given followed by an outline of the two main methods of forming colloidal photonic crystals employed by the authors’ research team- controlled evaporation (CE) which leads to face centred cubic structures such as are found in natural opal gemstones and the Langmuir-Blodgett (LB) method which leads to more disordered materials. The ability to control deposition on a layer-by-layer (LbL) level using the LB approach is highlighted by a discussion of the fabrication of a so-called AB heterostructured colloidal photonic crystal, made from spheres of two different sizes.

Following this the use of atomic layer deposition (ALD) to infill 3-D colloidal photonic crystals in order to be able to tune the refractive index contrast in the material is described, using as an example our work on the fabrication and characterisation of GaAs infilled colloidal photonic crystals and inverted GaAs photonic crystals that were made via infilling followed by removal of the silica host spheres. The importance of choosing the correct value for the refractive index of the infill material is highlighted and an optical Brillouin zone constructed using a free software package (MIT) which accounts for some of the observed Bragg reflections.

Finally, some examples are presented which demonstrate the potential of the use of these and other similar materials for a range of novel optical applications.

The paper reviews and discusses crystalline, nanocrystalline, glassy and amorphous chalcogenides and their thin films and fibres, their preparation, structure, properties, changes and applications in optics, optoelectronics and electronics, data storage and sensors with accent on recent data and progress. The area of interest is so broad that only some materials and processes could be discussed in detail, and a lot of data were chosen for the sake of illustration only.

Various ways of the preparation of crystalline, glassy and amorphous chalcogenides, their crystals, thin films and nanoparticles are mentioned; the structure, properties and applications of individual groups of materials are discussed. The applications are numerous: in the infrared technique, data storage, in light transformation and emission, in sensors, X-ray sensors, Xerox facilities, luminophors, lasers, ferroelectrics, thermoelectrics, catalysers, plasmonics materials; in topological insulators, fibres, in light up-conversion, nanodots and nanomaterials; in one-, two-, and three-dimensional systems, planar optical circuits, waveguides, non-linear optical and optomechanical devices, in surgical instruments, etc. Some of them are discussed in detail.

The review paper is based on several lectures presented on the occasion of “Nanomaterials and Nanoarchitectures International Summer School, Advanced Study Institute of NATO”, held in June/July 2013, in Cork, Ireland. The paper is primarily devoted to MSc. and Ph.D. students and postdoctoral students of solid state physics, solid state chemistry, material science and material engineering, but also to researchers as well as to general audience interested in science and technical progress, in order to help them understand and apply some of these materials and data.

Sensitive and robust detection of gases and chemical reactions constitutes a cornerstone of scientific research and industrial applications. In an effort to reach progressively smaller reagent concentrations and sensing volumes, optical sensor technology has experienced a paradigm shift from extended thin-film systems towards engineered nanoscale devices. In this size regime, plasmonic particles and nanostructures provide an ideal toolkit for the realization of novel sensing concepts. This is due to their unique ability to simultaneously focus light into subwavelength hotspots of the electromagnetic field and to transmit minute changes of the local environment back into the farfield as a modulation of their optical response. Since the basic building blocks of a plasmonic system are commonly noble metal nanoparticles or nanostructures, plasmonics can easily be integrated with a plethora of chemically or catalytically active materials and compounds to detect processes ranging from hydrogen absorption in palladium to the detection of trinitrotoluene (TNT). In this review, we will discuss a multitude of plasmonic sensing strategies, spanning the technological scale from simple plasmonic particles embedded in extended films to highly engineered complex plasmonic nanostructures. Due to their flexibility and excellent sensing performance, plasmonic structures may open an exciting pathway towards the detection of chemical and catalytic events down to the single molecule level.

The invention of hybrid crystals brought about the simultaneous usage of different mechanisms of light transfer into effect in one and the same architecture. We have discussed the preparation, structure and optical properties of planar hybrid metal-dielectric crystals, light in which is carried by photons and plasmons.

Studied hybrids are based on the monolayers of spheres – the planar hexagonal packages of colloidal beads on a substrate. Two basic modifications, the monolayer on a flat metal film and the corrugated metal film on the monolayer have been prepared. Owing to their topology, hybrid crystals respond to the incident light depending on the wavelength, the polarization and the propagation direction with different optical resonances. The respective resonances are the light diffraction in the planar lattice, the diffraction of surface plasmon polaritons in the periodically profiled film, the localized particle and cavity plasmons in metal semishells and Fabry-Perot oscillations. Besides, interpenetration of plasmonic and photonic crystals results in the efficient hybridization of photonic and plasmonic modes. Overlay of different resonances leads to their further modification described by Fano process.

The apparent complexity of the optical properties is paired by their broad variability either by means of tuning the topology and composition of hybrids or through external stimuli. The simple and inexpensive technology in combination with very rich physics ensures the attractiveness of hybrid crystals for fundamental research and practical applications.

In this Chapter we describe the experimental procedures and main features of solid organised films produced with three techniques: Langmuir-Blodgett (LB), electrostatic layer-by-layer (LbL) and self-assembled monolayers (SAMs). Emphasis is placed on possible applications in which molecular control of the film architectures is exploited. In particular, the use of organised films in sensing units for electronic tongues (e-tongues) and biosensors is highlighted not only in terms of the nanotech-based methods but also in connection with computational methods. The latter are employed in sensing and biosensing data analysis, and becoming increasingly important for generating fully-fledged clinical diagnosis systems. With regard to basic science involved in organised films, we discuss the use of Langmuir monolayers in cell membrane models, which is important for drug design and drug delivery systems.